This invention relates to intraluminal stent implants for maintaining patency of a body lumen in humans and animals and especially to such implants for use in blood vessels. The present invention comprises an improvement to stents which are generally cylindrical in shape and have a plurality of metal elements joined to permit flexing of the cylindrical body along the longitudinal axis of the body whereby the stent can conform to a curved body lumen. One such stent has metal elements made up of wire loops in a wound structure which allows individual loops to move with respect to one another. When a stent with this structure is expanded in a body lumen, the winding can follow curves in the body lumen. Such a stent is disclosed in U.S. Pat. No. 4,886,062 issued to Wiktor which is incorporated herein by reference. Another such stent is a stent having metal elements made up of individual stent segments joined together by hinges such that the hinges will allow the stent segments to adapt to curved body lumen. Such a stent is disclosed in published European Patent Application 0421729 by Wolff which is incorporated herein by reference. These stents can be deployed in a body lumen by means appropriate to their design. For example, in the case of the Wiktor stent, it can be fitted over the inflatable element of a balloon catheter and expanded by the balloon to force the stent into contact with the body lumen. Or, for example, in the case of the Wolff stent, it can be mounted onto a catheter which holds the stent as it is delivered through the body lumen and then releases the stent and allows it to expand into contact with the body lumen. This deployment is effected after the stent has been introduced percutaneously, transported transluminally and positioned at a desired location by means of the catheter.
An important use of these metal stents is found in situations where part of the vessel wall or stenotic plaque blocks or occludes blood flow in the vessel. Dilation of the blood vessel is usually undertaken to correct a blood vessel occlusion i.e., a balloon catheter is utilized in a PTCA procedure to enlarge the occluded portion of the blood vessel. However, the dilation of the occlusion can form flaps, fissures and dissections which threaten re-closure of the dilated vessel or even perforations in the vessel wall. Implantation of a metal stent can provide support for such flaps and dissections and thereby prevent reclosure of the vessel or provide a patch repair for a perforated vessel wall until corrective surgery can be performed. Moreover, such metal stents with good longitudinal flexibility can conform readily to vessels having curves and irregularities. However, such stents have limited ability to provide effective patching of perforated vessels due to the spacing between metal elements. Also, such metal stents also have limited ability to carry and deliver drugs, such as anti-restenosis drugs or anti-coagulant drugs, to the site of an intravascular injury.
In U.S. Pat. No. 4,878,906 issued to Lindeman et al., an endoprosthesis made of a thin wall molded plastic sleeve is disclosed, the sleeve is intended to be collapsed radially and delivered to a damaged area of a vessel where it is expanded to provide a sealed interface to the vessel on its outer peripheral ends. The endoprosthesis therefore provides a patch which prevents leakage of blood from a vessel wall. The endoprosthesis disclosed employs various molded-in ribs, struts and the like to adapt the device for particular applications and to provide the desired degree of stiffness to form the sealed interface with the vessel wall. However, such a stiff prosthesis could not be expected to have the longitudinal flexibility needed to adapt to curved vessels.
Polymeric stents which can also provide therapeutic substances to the vessel wall have also been proposed such as in published International Patent Application WO 91/12779 "Intraluminal Drug Eluting Prosthesis" In that application, it is suggested that antiplatelet agents, anticoagulant agents, antimicrobial agents, antimetabolic agents and other drugs could be supplied in polymeric stents to reduce the incidence of restenosis.
It is therefore an object of the present invention to provide a stent having longitudinal flexibility which allows it to conform to curves and variations in body lumens.
It is also an object of the present invention to provide a stent capable of patching leaking blood vessels.
It is also an object of the present invention to provide a stent capable of delivering therapeutic agents to a blood vessel.